सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

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ecliptic successively each of 30°, we have what are called
Sāyana Rasis or Rasis taking the Ayanāṁsa into consi-
deration or in other words measuring from r. On the
other hand successive arcs each of 30° measured from the
zero point of the Hindu Zodiac, constitute what are called
the Nirayana Rāśis. The words Meṣa, Vṛṣabha etc.
signifying the shapes of the constellations apply strictly
to the Nirayana Rāśis. But nonetheless, by the conven-
tion what is called Upachāra, we name the Sāyana Rāśis
also by the same names. In as much as the zero-points
of the Hindu Zodiacs is ahead of the modern zero-point by
an arc which is the arc of Ayanamsa or accumulated pre-
cession, the words Sāyana and Nirayana came into vogue.
Once upon a time approximately in Varāha’s time or
rather 499 A. D, the two zero-points coincided and then
the Sāyana and Nirayana Rāśis were the same. Gradually
on account of the phenomenon of precession r preceded,
and today the distance between r and the Hindu zero-
point is about 20°–30′. Of late, there has been a big
controversy as to what exactly the arc is and the Calendar
reform committee has adopted a value far more than what
could be justified. The present author opines, that we
have no right to set aside a statement of no less an astro-
nomer than Varāhamihira who stated explicity ‘आश्लेषार्धात्
दक्षिणमुत्तरमयनं रखेर्धनिष्ठाद्यम् , नूनं कदाचिदासीत् येनोक्तंपूर्वशास्त्रेषु,
साम्प्रतमयनं सवितुः कर्कटकाद्यं मृगादितश्चाऽन्यत् उक्ताभावो विकृतिः
प्रत्यक्षपरीक्षणव्यक्तिः” i.e. True it is that once upon a time,
the Sun began his southern journey when he was mid-way
the constellation of Asleṣa and his northern when he was
at the beginning of Dhaniṣtha, because it was stated in
ancient texts. (The allusion is to Vedāṅga Jyotiṣa
where it was stated as such); but now the southern journey
of the Sun begins from the point marking ¾ of the con-
stellation of punarvasu which is the beginning point of
the Karkaṭa Rāśi and his norther from the beginning of
Makara i.e. from the point marking ¼th of the constellation
of Uttarāṣādha; there has been a change from what was